Three in One or 3-in-1 may refer to:

• 3-In-One Oil, a general-purpose lubricating oil
• Three in One (film), a 1957 Australian anthology film
• Three in One, high-occupancy vehicle lane in Indonesia
• 3 in 1, 2012 album by Wali
• 3-in-1 (fast food dish), an Irish dish consisting of chips, rice and curry sauce
• The Christian concept of the Trinity